I will have been married for 8 years this June. Sure we've dissagreed at times, any relationship where you never dissagree is either very new or someone is being dominated. The key to making it last however is to realize that this IS the most important thing in your life. Just because you are married doesn't mean you're "off the hook". You still need to do the things you did when you we're dating. Heck, you still need to date! Get out once a week, make time for each other! AND DON'T FORGET TO TALK! Nothing will destroy a relationship faster then apathy. And if you have stopped it's never to late to start. Start dating, start talking, start careing.
All that said, I wouldn't trade my husband and kids for anything. It's worth every bit of my time and effort and I am very lucky to have them.